Preparation of porous super-hydrophobic and super-oleophilic polyvinyl chloride surface with corrosion resistance property

Porous super-hydrophobic polyvinyl chloride (PVC) surfaces were obtained via a facile solvent/non-solvent coating process without introducing compounds with low surface energy. The microstructure, wetting behavior, and corrosion resistance of resultant super-hydrophobic PVC coatings were investigated in relation to the effects of dosage of glacial acetic acid and the temperature of drying the mixed PVC solution spread over glass slide substrate. As-prepared PVC coatings had porous microstructure, and the one obtained at a glacial acetic acid to tetrahydrofuran volume ratio of 2.5:10.0 and under a drying temperature of 17 °C had a water contact angle of 150 ± 1.5°, showing super-hydrophobicity. In the meantime, it possessed very small contact angles for liquid paraffin and diiodomethane and good corrosion resistance against acid and alkali corrosive mediums, showing promising applications in self-cleaning, waterproof for outer wall of building, seawater resistant coating, and efficient separation of oil and water.     

Novel strategy in increasing stability and corrosion resistance for super-hydrophobic coating on aluminum alloy surfaces

A novel super-hydrophobic coating was prepared by chemical modification on the anodized aluminum alloy surface. The surface structure was characterized by water contact angle measurement, scanning electron microscopy (SEM), and the composition was measured by X-ray photoelectron spectroscopy (XPS). The corrosion behavior of the super-hydrophobic coating was evaluated by the polarization curve and the electrochemical impedance spectroscopy (EIS). It was found that the static water contact angle on the surface of super-hydrophobic coating was as high as 167.7 ± 1.2°, and the sliding angle was 5°. The super-hydrophobic coating resulted in excellent corrosion resistance property and the super-hydrophobic coating showed a good stability.     

Preparation and properties of super-hydrophobic coating on magnesium alloy

The super-hydrophobic coating was successfully fabricated on the surface of magnesium alloy AZ31 by chemical etching and surface modification. The surface morphologies, compositions, wettability and corrosion resistance of the coating were investigated with SEM, XPS, contact angle measurement and electrochemical method, respectively. It shows that the rough and porous micro-nano-structure was presented on the surface of magnesium alloy, and the contact angle could reach up to 157.3 ± 0.5° with sliding angle smaller than 10°. The super-hydrophobic coating showed a long service life. The results of electrochemical measurements showed that anticorrosion property of magnesium alloy was improved. The super-hydrophobic phenomenon of the prepared surface was analyzed with Cassie theory, and it finds that only about 10% of the water surface is contacted with the metal substrate and the rest 90% is contacted with the air cushion.     

Preparation of hybrid film with superhydrophobic surfaces based on irregularly structure by emulsion polymerization

A superhydrophobic surface originated from quincunx-shape composite particles was obtained by utilizing the encapsulation and graft of silica particles to control the surface chemistry and morphology of the hybrid film. The composite particles make the surface of film form a composite interface with irregular binary structure to trap air between the substrate surface and the liquid droplets which plays an essential role in obtaining high water contact angle and low water contact angle hysteresis. The water contact angle on the hybrid film is determined to be 154 ± 2° and the contact angle hysteresis is less than 5°. This is expected to be a simple and practical method for preparing self-cleaning hydrophobic surfaces on large area.     

Extreme wettability due to dendritic copper nanostructure via electrodeposition

Dendritic copper film with convertible extreme wettability is prepared on metal surface via electrodeposition. With field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and electrochemical measurement, the morphology, composition and formation mechanism of dendritic copper film were studied. It is found that the film is mainly composed of metallic copper. Also some residual cuprous oxide and chloride exist in the deposit. The single micron-sized dendrite consists of a main stem with side branches, on which the higher-order branches with the dimension of tens of nanometers grow. A hydrophobic modification can induce the conversion of the apparent wettability of film from super-hydrophilicity (with apparent water contact angle of 5 ± 3°) to super-hydrophobicity (with apparent water contact angle of 154.1 ± 3°), which is due to the capillary effect. The method proposed in this paper is time-saving and facile to operate, and it offers a promising technique to prepare metallic surface with a high wettability contrast for water.     

A novel method to fabricate water-soluble hydrophobic agent and super-hydrophobic film on pretreated metals

This paper demonstrated a convenient method to prepare water-soluble hydrophobic agent and create super-hydrophobic film on the basic material of phosphating film and electroless Ni-P composite coating on carbon steels. Water contact angles and rolling angles of super-hydrophobic films were 155-168° and 2-3° on phosphating films, respectively, 145-155° and 15-20° on electroless Ni-P composite coatings, respectively. This water-soluble hydrophobic agent was white latex and had lots of micro-particles suspending in it. The thickness of the single-layer super-hydrophobic film with good corrosion resistance and stability was about 2-3 μm. The microstructure of super-hydrophobic film was discussed using XRD, EDS, optical and electronic microscope as analytical methods. This kind of super-hydrophobic film had a great many micro-particles dispersing in the surface, which contained F and Si and greatly increased the roughness of the surface.     

Effect of plasma pretreatment on adhesion and mechanical properties of UV-curable coatings on plastics

An attempt was made to study the effect of plasma surface activation on the adhesion of UV-curable sol-gel coatings on polycarbonate (PC) and polymethylmethacrylate (PMMA) substrates. The sol was synthesized by the hydrolysis and condensation of a UV-curable silane in combination with Zr-n-propoxide. Coatings deposited by dip coating were cured using UV-radiation followed by thermal curing between 80 °C and 130 °C. The effect of plasma surface treatment on the wettability of the polymer surface prior to coating deposition was followed up by measuring the water contact angle. The water contact angle on the surface of as-cleaned substrates was 80° ± 2° and that after plasma treatment was 43° ± 1° and 50° ± 2° for PC and PMMA respectively. Adhesion as well as mechanical properties like scratch resistance and taber abrasion resistance were evaluated for coatings deposited over plasma treated and untreated surfaces.     

Super-hydrophobic nickel films with micro-nano hierarchical structure prepared by electrodeposition

Super-hydrophobic nickel films were prepared by a simple and low cost electrodepositing method. The surface morphologies of the films characterized by scanning electronic microscope exhibit hierarchical structure with micro-nanocones array, which can be responsible for their super-hydrophobic characteristic (water contact angle over 150°) without chemical modification. The wettability of the film can be varied from super-hydrophobic (water contact angle 154°) to relatively hydrophilic (water contact angle 87°) by controlling the size of the micro-nanocones. The mechanism of the hydrophobic characteristic of nickel films with this unique structure was illustrated by several models. Such micro-nanostructure and its special wettability are expected to be applied in the practical industry.     

Structural, morphological, wettability and thermal resistance properties of hydro-oleophobic thin films prepared by a wet chemical process

The structural properties of fluorine containing polymer compounds make them highly attractive materials for hydro-oleophobic applications. However, most of these exhibit low surface energy and poor adhesion on the substrates. In the present investigation, crack free, smooth and uniform thin films of poly[4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole]-co-tetrafluoroethylene (TFD-co-TFE) with good adhesion have been deposited by wet chemical spin-coating technique on polished AISI 440C steel substrates. The as-deposited films (xerogel films) have been subjected to annealing for 1 h at different temperatures ranging from 100 to 500 °C in an argon atmosphere. The size growth of the nano-hemispheres increased from 8 nm for xerogel film to 28 nm for film annealed at 400 °C. It was found that as the annealing temperature increased from 100 to 400 °C, nano-hemisphere-like structures were formed, which in turn have shown increase in the water contact angle from 122° to 147° and oil (peanut) contact angle from 85° to 96°. No change in the water contact angle (122°) has been observed when the films deposited at room temperature were heated in air from 30 to 80 °C as well as exposed to steam for 8 days for 8 h/day indicating thermal stability of the film.     

Investigation of in-plane orientation characteristics for Bi-2212/MgO thin films fabricated by the MOD method

We investigated the characteristics of in-plane orientation for c-axis-oriented Bi-2212 thin films on MgO substrates, fabricated by the metal–organic decomposition (MOD) method. Bi-2212/MgO films were annealed using a 2-step heat treatment. The dominant rotation angle of the Bi-2212 film was 45° ([1 0 0] of Bi-2212 // [1 1 0] of MgO) for a precursor film fabricated at 500 °C and fired at 840 °C for 0 min or 30 min. However, after firing for 1 h the ?-scanning signal indicating the 45° angle became smaller and the signal representing an angle of about ±12° ([1 0 0] of Bi-2212 // [5 1 0] of MgO) became larger. After firing for 3 h, this ±12° signal became dominant. The extent of the 45° angle’s shift to ±12° increased with increasing firing time. On the other hand, when the precursor film was fabricated at 430 °C, signals indicating angles of 0°, ∼±12°, and 45° were observed after firing for 30 min. The rotation angle depended on the precursor-fabrication temperature when the precursor film was fired at 840 °C for 0 min or 30 min.     

Superhydrophobic poly(vinylidene fluoride) film fabricated by alkali treatment enhancing chemical bath deposition

Based on the lotus effect principle, the superhydrophobic poly(vinylidene fluoride) (PVDF) film was successfully prepared by the method of alkali treatment enhancing chemical bath deposition. The surface of PVDF film prepared in this work was constructed by many smooth and regular microreliefs. Oxygen-containing functional groups were introduced in PVDF film by treatment with aqueous NaOH solution. The nano-scale peaks on the top of the microreliefs were implemented by the reaction between dimethyldichlorosilane/methyltrichlorosilane solution and the oxygen-containing functional groups of PVDF film. The micro- and nano-scale structures, similar to the lotus leaf, was clearly observed on PVDF film surface by scanning electronic microscopy (SEM) and atomic force microscope (AFM). The water contact angle and sliding angle on the fabricated lotus-leaf-like PVDF film surface were 157° and 1°, respectively, exhibiting superhydrophobic property and self-cleaning property.     

Structural, compositional, thermal resistant and hydro-oleophobic properties of fluorine based block-co-polymer films on quartz substrates by wet chemical process

Crack free and smooth surfaces of poly [4,5-difluoro 2,2-bis (trifluoromethyl)-(1,3 dioxole)-co-tetrafluoroethylene] (TFE-co-TFD) thin films have been deposited by wet chemical dip coating technique on polished quartz and glass slide substrates. The deposited films have been subjected to annealing at different temperatures ranging from 100 to 500 °C for 1 h in argon atmosphere. The elemental composition of the as-deposited (xerogel) thin film as well as film annealed at 400 °C was measured by X-ray photoelectron spectroscopy and observed that there was no change in the composition of the film. X-ray diffraction pattern revealed the amorphous behaviour of both as-deposited and film annealed at 400 °C. Surface morphology and elemental composition of the films have been examined by employing scanning electron microscopy attached with energy dispersive X-ray analyser, respectively. It was found that as the annealing temperature increased from 100 to 400 °C, nano-hemisphere-like structures have been grown, which in turn has shown increase in the water contact angle from 122^o to 148^o and oil (peanut) contact angle from 85° to 96°. No change in the water contact angle (122°) has been observed when the films deposited at room temperature were heated in air from 30 to 80 °C as well as exposed to steam for 8 days for 8 h/day indicating thermal stability of the film.     

Highly hydrophobic and oleophilic foam for selective absorption

In this article, both highly hydrophobic and oleophilic foam were fabricated by coating inner surface of polyurethane (PU) foam with a super-hydrophobic film. The contact angle of the foam is large as 152.2° for water, and 0° for kerosene. The foam can absorb kerosene selectively from kerosene-water mixture and be regenerated easily. The foam may be used to reclaim oil from polluted natural water area resulted from shipwreck or leakage.     

The fabrication of superhydrophobic copper films by a low-pressure-oxidation method

The lotus-leaf-like superhydrophobic copper was fabricated by a facile two-step method without the chemical modification, on which the water contact angle can reach 158° and the water-sliding angle is less than 10°. Reversible superhydrophobicity to superhydrophilicity transition was observed and controlled by alternation of UV irradiation and dark storage. More interestingly, the superhydrophobic surface exhibits superoleophilicity and all those properties can be well used in reversible switch, separating the water and oil and so on.     

Super-hydrophobic surface on pure magnesium substrate by wet chemical method

A layer of flower-like super-hydrophobic film was fabricated on pure Mg surface by chemical etching in H₂SO₄, H₂O₂ and subsequent immersion in stearic acid (CH₃(CH₂)₁₆COOH) ethanol solution. The super-hydrophobic surface showed a static water contact angle of 154° with the sliding angle of about 3°. With scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and Fourier-transform infrared (FT-IR) spectrometer, the microstructure and composition of the sample were analyzed. Results showed that the flower-like structure and the bonding of the CH₃(CH₂)₁₆COO⁻ on Mg surface can be responsible for the superior water-repellent property. Electrochemical impedance spectroscopy revealed that the transfer resistance of super-hydrophobic surface was increased about four times than bare Mg after one-hour immersion in 0.1 mol/L NaCl solution.     

Nanocrystalline nickel films with lotus leaf texture for superhydrophobic and low friction surfaces

Nanostructured Ni films with high hardness, high hydrophobicity and low coefficient of friction (COF) were fabricated. The surface texture of lotus leaf was replicated using a cellulose acetate film, on which a nanocrystalline (NC) Ni coating with a grain size of 30 ± 4 nm was electrodeposited to obtain a self-sustaining film with a hardness of 4.42 GPa. The surface texture of the NC Ni obtained in this way featured a high density (4 × 10³ mm⁻²) of conical protuberances with an average height of 10.0 ± 2.0 μm and a tip radius of 2.5 ± 0.5 μm. This structure increased the water repellency and reduced the COF, compared to smooth NC Ni surfaces. The application of a short-duration (120 s) electrodeposition process that deposited “Ni crowns” with a larger radius of 6.0 ± 0.5 μm on the protuberances, followed by a perfluoropolyether (PFPE) solution treatment succeeded in producing a surface texture consisting of nanotextured protuberances that resulted in a very high water contact angle of 156°, comparable to that of the superhydrophobic lotus leaf. Additionally, the microscale protuberances eliminated the initial high COF peaks observed when smooth NC Ni films were tested, and the PFPE treatment resulted in a 60% reduction in the steady-state COFs.     

Conciliating surface superhydrophobicities and mechanical strength of porous silicon films

Hydrophobic surfaces on Mechanical stable macroporous silicon films were prepared by electrochemical etching with subsequent octadecyltrichlorosilane (OTS) modification. The surface morphologies were controlled by current densities and the mechanical properties were adjusted by their corresponding porosities. Contrast with the smooth macroporous silicon films with lower porosities (34.1%) and microporous silicon with higher porosities (97%), the macroporous film with a rough three-dimension (3D) surface and a moderate pore to cross-section area ratio (37.8%, PSi2′) exhibited both good mechanical strength (Yong’ modulus, shear modulus and collapse strength are 64.2, 24.1 and 0.32 GPa, respectively) and surface superhydrophobicity (water contact angle is 158.4 ± 2° and sliding angle is 2.7 ± 1°). This result revealed that the surface hydrophobicities (or the surface roughness) and mechanical strength of porous films could be conciliated by pore to cross-section area ratios control and 3D structures construction. Thus, the superhydrophobic surfaces on mechanical stable porous films could be obtained by 3D structures fabrication on porous film with proper pore to cross-section area ratios.     

Surface modification of porous poly(tetrafluoraethylene) film by a simple chemical oxidation treatment

A simple, inexpensive and environmental chemical treatment process, i.e., treating porous poly(tetrafluoroethylene) (PTFE) films by a mixture of potassium permanganate solution and nitric acid, was proposed to improve the hydrophilicity of PTFE. To evaluate the effectiveness of this strong oxidation treatment, contact angle measurement was performed. The effects of treatment time and temperature on the contact angle of PTFE were studied as well. The results showed that the chemical modification decreased contact angle of as-received PTFE film from 133 ± 3° to 30 ± 4° treated at 100 °C for 3 h, effectively converting the hydrophobic PTFE to a hydrophilic PTFE matrix. The changes in chemical structure, surface compositions and crystal structure of PTFE were examined by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD), respectively. It was found that the F/C atomic ratio decreased from untreated 1.65-0.10 treated by the mixture at 100 °C for 3 h. Hydrophilic groups such as carbonyl (CO) and hydroxyl (OH) were introduced on the surface of PTFE after treatment. Furthermore, hydrophilic compounds K_0.27MnO₂·0.54H₂O was absorbed on the surface of porous PTFE film. Both the introduction of hydrophilic groups and absorption of hydrophilic compounds contribute to the significantly decreased contact angle of PTFE.     

An approach towards the growth of polyaniline nanograins by electrochemical route

The growth of electropolymerized polyaniline nanograins has been carried out from aqueous solution of 0.45 M aniline (C₆H₅NH₂) + 0.5 M H₂SO₄. These polyaniline nanograins were characterized using Raman spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), contact angle measurement and optical studies. The presence of characteristic bonds of polyaniline was observed from Raman shift experiment. Based on field emission scanning electron microscopy and transmission electron microscopy analysis, the formation of the polyaniline nanograins with average diameter of about 50 nm was inferred. Surface of the polyaniline film was hydrophilic with contact angle 17 ± 1°. A blue shift of 0.30 eV with characteristic absorption peak at 427 nm has been attributed due to quantized size of polyaniline nanograins.     

Enhanced cell affinity of poly(l-lactide) film by immobilizing phosphonized chitosan

Graft polymerization of acrylic acid (AA) onto poly(l-lactide) (PLLA) film by UV irradiation was carried out to develop surfaces for N-methylene phosphonic chitosan (NMPC) immobilization. The properties of modified films were discussed by colorimetric method, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), contact angles, atomic force microscopy (AFM) and osteoblast incubation. The results showed that AA solution concentration and irradiation time had effect on the graft carboxyl densities. Comparing the ATR-FTIR images, two new peaks at 1561 cm⁻¹ and 1632 cm⁻¹ proved that NMPC was immobilized on the film surface successfully. The water contact-angles were decreased from 90 ± 5° to 37 ± 5° after modification. The AFM images indicated that the surface of the combined film was rougher than that of untreated film. The grafted film provided an excellent substrate for the growth of osteoblast.